Any one that will fit? That's really a pretty broad question and it has more to deal with your abilities and what you want to make. And there is always the old maxim, "There is more than one way to skin a cat"I'm extremely biased, so I'm going to say any thing that runs Linux for the heavy lifting (inverse kinesmatics, computer vision, sensor fusion and state estimation) and can communicate with an AVR (for all the hard I/O like analog In and pwm out). So off the top of my head I'd go with these two products to tackle the widest set of problems you may encounter: